Collagen is a general term describing a variety of naturally occurring proteins found in animals, especially in the flesh and connective tissues. It is considered to be the most abundant protein in mammals, comprising 25% to 35% of the whole body protein.
The most abundant form of collagen is believed to be Type I collagen, which is found in skin, tendons, vascular ligature, organ, and bones. Type I collagen appears to comprise over 90% of the total collagen in the body. The commonly accepted model characterizes type I collagen as a fibrillar form of collagen, composed of three polypeptide strands in a triple helix. The triple helices are further associated into coiled coils, which are associated further into super coils referred to as collagen microfibrils, These microfibrils are interdigitated with other microfibrils,forming collagen fibrils which can be so well ordered as to be crystalline in some respects.
Isolated collagen has many uses, and a wide variety of techniques have been developed to isolate the collagen. These techniques can have very different effects on the structure of the collagen, and on the form which is isolated. Treatment with strong acids and bases can hydrolyze the cross-links and other intermolecular structures which hold the polypeptide strands to each other, generating the viscous, water-soluble form of collagen known as gelatin. Cioca et al appears to teach treatment with enzymes such as casein to isolate forms of collagen for the manufacture of artificial chamois (Cioca et al, U.S. Pat. No. 4,327,195, 1982). Acid extraction of calf tendons has been proposed to prepare a biocompatible fluid containing acid-soluble collagen for injection. (Kemp et al, U.S. Pat. No. 5,106,949, 1992). These preparations of soluble collagens would be expected to denature the collagen, resulting in the disruption of the intermolecular bonding and of the fibril and microfibril structure of the collagen.
Insoluble forms of collagen I are typically produced by mechanical methods which avoid disruption of the intermolecular collagen bonding. One method proposed is a combination of simple cutting and grinding processes (eg Aceto et al, 3,665,998, 1972), and the resulting particulate collagen may be formed into structures by, for example, suspension and freeze-drying (eg Cioca, 4,412,947, 1983).
When refined to a small enough particle size, it has been reported that the natural structure of even “insoluble” collagen may be reduced to the point that it exhibits some solubility in strong solvents such as dimethyl sulfoxide and dimethyl formamide. In many cases, these materials can also be handled in water dispersions. The use of very small particles of lower molecular weight collagens (less than 0.5 millimeter particles for molecular weights less than 30,000, for example) has been reported to improve the properties of hydrophobic polyurethane foams when used as a filler material. (Cioca et al, U.S. Pat. No. 4,327,195, 1985). Processing of the collagen to the extent required for this type of handling, however, may denature it to the point that the natural elasticity, flexibility, strength and stability of the collagen fibers is reduced.
In light of the number of techniques for processing collagen which denature the protein, the advantages of a dean, non-denatured collagen in combination with a polymer foam have yet to be realized. There is still a need, therefore, for a sponge that incorporates non-denatured collagen fibers.
Collagen has been used in cosmetics applications both intradermally (by injection) and extrader ally (by application to the surface of the skin). Reportedly, one of the mechanisms of the visible appearance of skin aging is the loss of collagen, resulting in a reduction of the soft tissue and formation of wrinkles. Injectable collagen compositions (eg Janzen et al, U.S. Pat. No. 5,523,291, 1996) have been proposed for soft tissue augmentation, to reduce visible wrinkling in aging skin or to reduce the appearance of scarring, and to augment features such as lips and cheeks. Cosmetic creams may contain hydrolyzed collagen for use as moisturizers or to reduce the visible appearance of wrinkles and lines. Other skin treatments, including pastes and foils (eg Braumer et al, U.S. Pat. No. 4,131,650, 1978) may include soluble collagen in a form which can be transported to and absorbed by the skin. The lack of a fibrillar structure in these hydrolyzed collagen products, however, typically results in reabsorption of the collagen into the body and destruction by collagenase, requiring frequent reapplication of the treatments.
There is also a need, therefore, for a non-hydrolyzed, non-denatured collagen which can be applied extradermally, and for a convenient form in which to apply that material.
What is desired is a cosmetic sponge and a method for providing a cosmetic sponge that benefits from the properties grip ted from the incorporation of a non-denatured collagen, and for a cosmetic sponge that can apply a beneficial form of non-denatured collagen to the skin.